GB2570678A - Electrochemical device and inorganic fibres for use therein - Google Patents

Electrochemical device and inorganic fibres for use therein Download PDF

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Publication number
GB2570678A
GB2570678A GB1801684.0A GB201801684A GB2570678A GB 2570678 A GB2570678 A GB 2570678A GB 201801684 A GB201801684 A GB 201801684A GB 2570678 A GB2570678 A GB 2570678A
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Prior art keywords
lithium
inorganic
separator
separator according
fibres
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GB201801684D0 (en
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Brown Martyn
Clark Richard
Peter Street Jason
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Thermal Ceramics UK Ltd
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Thermal Ceramics UK Ltd
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Priority to GB1801684.0A priority Critical patent/GB2570678A/en
Publication of GB201801684D0 publication Critical patent/GB201801684D0/en
Priority to CN201980009381.0A priority patent/CN111630688A/en
Priority to EP19702698.2A priority patent/EP3747067A1/en
Priority to KR1020207021651A priority patent/KR20200112855A/en
Priority to PCT/GB2019/050222 priority patent/WO2019150083A1/en
Priority to GB1901343.2A priority patent/GB2568613B/en
Priority to US16/263,258 priority patent/US11264614B2/en
Publication of GB2570678A publication Critical patent/GB2570678A/en
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/52—Separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/431—Inorganic material
    • H01M50/434—Ceramics
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/004—Details
    • H01G9/02—Diaphragms; Separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
    • H01M10/0562—Solid materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/44—Fibrous material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/13—Energy storage using capacitors

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Power Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Materials Engineering (AREA)
  • Cell Separators (AREA)
  • Secondary Cells (AREA)

Abstract

A separator for an electrochemical device comprises lithium ion conducting inorganic fibres. The separator may comprise 5 to 100 wt% lithium ion conducting inorganic fibres; 0 to 95 wt% lithium ion conducting inorganic particles; and 0 to 50 wt% binder. The inorganic content is preferably at least 90 wt%, and the inorganic fibres preferably comprise a lithium content greater than 1.0 wt%. A number of different options for the material of the inorganic fibres are disclosed, including a mixture of Li2O, Al2O3 and SiO2, and the lithium aluminium silicates eucryptite (LiAlSiO4), spodumene (LiAl(SiO3)2) and pettulite (LiAlSi4O10), with eucryptite being preferred. The inorganic fibres can be made using sol-gel, melt-spinning or electrospinning techniques. The separator may form a composite membrane or matrix with a solid, gel or liquid electrolyte. The separator is preferably used in a Li-ion battery, but may also be used in a capacitor, especially a supercapacitor. Also disclosed is the use of the inorganic fibres in a solid electrolyte or an inorganic/organic electrolyte matrix.

Description

The present invention relates to electrochemical devices and components thereof which comprise lithium ion conducting fibres.
Background to the Invention
During charging of a lithium-ion electrochemical cell, electrons flow from an external voltage source and lithium cations flow through the electrolyte toward the anode. When the cell is discharged, the lithium cations flow through the electrolyte and the electrons flow from the anode material to the cathode material through a load.
In order to avoid a short circuit within the electrochemical cell, a layer which is electrically insulating but permeable to lithium cations is located between the two electrodes. This is known as a separator, which can be of a conventional form such as a thin polymeric material, a ceramic-coated polymeric material, a ceramic-polymer composite, a non-woven fabric, each of which are immersed in the liquid electrolyte or a solid electrolyte which fills the space between anode and cathode in entirety either as a solid ceramic material or as a ceramic material dispersed within an organic polymer.
Separators must resist mechanical stresses and this poses no problems for conventional separator films based, for example, on polyolefins, at the thicknesses at which they are used.
A demand for high power densities has placed increasing demands upon the performance of separators. Polyolefin separators have current shutdown characteristics within a temperature range of typically from 130 to 170°C as the micropores close in this temperature range and this is intended to prevent further flow of lithium cations across the separator.
However, in batteries, which have larger surfaces, for example large format batteries, the chance for short circuit increases, since the melting of the polyolefin is not uniform across its full area at an elevated temperature and when one area melts, it actually increases the likelihood of failure in an adjacent area because of the consequent increase in current density
Zhao et al, Inorganic ceramic fibre separator for electrochemical and safety performance improvement of lithium ion batteries, Ceramics International 43 (2017), 14775-14783, reported separators comprising inorganic components with high thermal stability leading to enhanced safety performance resultant batteries. Despite this, there is still a demand for high performance battery separator and the like to drive higher performance in lithium ion batteries.
Summary of the Invention
In a first aspect of the present invention there is provided an electrochemical device comprising lithium ion (Li-ion) conducting inorganic fibres. The fibres may be woven or nonwoven, aligned or randomly orientated.
Any lithium ion containing composition may be used which can be incorporated into an inorganic fibre.
The electrochemical device is preferably a lithium ion battery, although in some embodiments the electrochemical device may comprise a capacitor, including a super capacitor.
It will appreciated that the inventive concept may be applied to other metal ion battery chemistries including magnesium, aluminium or sodium ion batteries. As such, the inventive concept extends to all metal ion electrochemical devices comprising the associated metal ion conducting inorganic fibres. Many of the inorganic fibres compositions can be readily converted to the corresponding metal ion composition through the stoichiometric replacement of lithium ions with alternative metal cations, such as aluminium, magnesium or sodium.
The incorporation of lithium ion conducting inorganic fibres within electrochemical devices enable lithium ion mobility through the inorganic fibre lattice, either within a separator and/or within the electrolyte itself.
The incorporate of lithium ion conducting inorganic fibres enables lithium ion electrochemical devices to have increased design freedom. The inorganic fibres are able to enhance mechanical and high temperature robustness of the devices, with the use of inorganic fibres as an electrolyte also having the potential to avoid or lessen lithium dendrite formation.
In a second aspect of the present invention, there is provided a process to produce the inorganic fibres of the first aspect of the present invention using sol-gel, melt spun or electrospinning techniques.
In a third aspect of the present invention there is provided inorganic fibres as defined in the first aspect of the present invention. The inorganic fibres are preferably for use in a separator; a solid electrolyte or an inorganic I organic electrolyte matrix.
In a fourth aspect of the present invention, there is provided a separator comprising the inorganic fibres as defined in the first aspect of the present invention.
In a fifth aspect of the present invention, there is provided a solid electrolyte comprising the inorganic fibres as defined in the first aspect of the present invention.
In a sixth aspect of the present invention, there is provided an inorganic fibre I organic electrolyte matrix. The formation of a matrix comprising lithium ion conducting inorganic fibres I lithium ion conducting electrolyte (solid or liquid) may result in electrochemical devices which comprise lithium ion conducting pathways between electrodes which may be partially through organic electrolytes (solid and/or liquid) and partially through inorganic electrolytes (including lithium ion conducting inorganic fibres). In some embodiments, the lithium ion conducting pathways between the electrodes may be continuously through inorganic electrolytes. Inorganic particles may be added to the matrix to increase the number of lithium ion pathways through the inorganic component of the matrix. The addition of inorganic particles may also enable the proportion of the inorganic component in the matrix to increase.
The matrix preferably comprises:
to 80wt% and preferably 10 to 40wt% lithium ion conducting inorganic fibres to 40wt% and preferably 5 to 20wt% lithium ion conducting inorganic particles to 95wt% and preferably 40 to 80wt% lithium ion conducting organic electrolytes Li-ion conducting inorganic fibres provide a unique combination of mechanical strength, high temperature and chemical stability, whilst enhancing lithium-ion conductivity within the electrochemical device relative to conventional polymeric or inorganic fibres used within electrochemical devices.
The Li-ion conducting inorganic fibres preferably comprise compositions selected from the groups including lithium oxide, lithium silicate, lithium phosphate (U3PO4), lithium aluminate, lithium aluminium silicates, lithium borates, lithium zirconium silicates, lithium alkaline earth silicates, lithium zirconium/titanium phosphates, lithium lanthanum zirconates/titanates and combinations thereof.
The composition of the inorganic fibres preferably comprises at least 1.0 wt% lithium, more preferably at least 2.0 wt% or at least 5.0 wt% or at least 8.0 wt % or at least 10 wt% or at least 12 wt% or at least 15 wt% or at least 20 wt % or at least 25 wt% or at least 30 wt% lithium. Higher lithium contents tend to favour higher ionic conductivity. The lithium content is preferably less than 50wt% or 40 wt% or 30wt%. Too high a lithium content may affect the ability to form a fibre of sufficient mechanical properties.
The composition preferably further comprises the oxide forms of boron, sodium, magnesium, aluminium, silicon, phosphorus, potassium, gallium, strontium, zirconium, barium, lanthanum, calcium, vanadium, manganese, iron, cerium, niobium, titanium and combinations thereof. Hafnium may be present as an impurity, particularly when the composition comprises zirconium. The sum of the abovementioned oxides is preferably at least 90mol% and more preferably at least 95mol%. Additional components are preferably only present as impurities.
The compositions of the inorganic fibres are preferably within 25%, more preferably within 15% and even more preferably within 5% of the stoichiometric formulas of the lithium compound crystalline forms.
Preferred lithium silicates include the crystalline and/or amorphous form of Li2SiO3 or Li2SiO4 and combinations thereof.
A preferred composition of lithium silicate fibres comprise:
to 30wt% and more preferably 4 to 20wt% U2O; and to 80 wt% and more preferably 20 to 70 wt% SiC>2.
The sum of U2O + S1O2 is preferably greater than 50 wt%, more preferably greater than 80wt% and even more preferably greater than 95wt%.
Preferred lithium aluminates include the crystalline and/or amorphous form of UAIO2 or U2AI2O4 and combinations thereof.
A preferred composition of lithium aluminate fibres comprise:
to 30wt% and more preferably 4 to 20 wt% U2O; and to 80 wt% and more preferably 20 to 70 wt% AI2O3.
The sum of U2O + AI2O3 is preferably greater than 50 wt%, more preferably greater than 80wt% and even more preferably greater than 95 wt%.
Preferred lithium aluminium silicates include the crystalline and/or amorphous form of LisAhSiOs, LiAISi2C>6, LiAISi40w or LiAISiCU and combinations thereof.
A preferred composition of lithium aluminium silicates fibres comprise:
to 20wt% and more preferably 4 to 15wt% U2O;
to 75 wt% and more preferably 15 to 65 wt% AI2O3; and to 80 wt% and more preferably 25 to 70 wt% S1O2
The sum of U2O + AI2O3 + S1O2 is preferably greater than 50 wt%, more preferably greater than 80wt% and even more preferably greater than 95wt%.
Preferred lithium aluminium zirconates include the crystalline and/or amorphous form of Li7AhZr20i2.
A preferred composition of lithium aluminium zirconate fibres comprise:
to 40wt% and more preferably 10 to 30wt% U2O;
to 50 wt% and more preferably 15 to 40wt% AI2O3;
to 65 wt% and more preferably 30 to 50 wt% ZrO2.
The sum of Li2O + AI2C>3 + ZrO2 is preferably greater than 50 wt%, more preferably greater than 80wt% and even more preferably greater than 95wt%.
Preferred lithium borates include the crystalline and/or amorphous form of I^BeOn,
Li3(BO2)3, Li2B4O7or LiBO2 and combinations thereof.
A preferred composition of lithium borate fibres comprise:
to 50wt% and more preferably 15 to 40wt% Li2O; and to 80 wt% and more preferably 20 to 70 wt% B2C>3
The sum of Li2O + B2C>3 is preferably greater than 50 wt%, more preferably greater than 80wt% and even more preferably greater than 95wt%.
Preferred lithium zirconium silicates include the crystalline and/or amorphous form of Li2ZrSi60i5 and combinations thereof.
A preferred composition of lithium zirconium silicates fibres comprise:
to 30wt% and more preferably 5 to 25wt% Li2O;
to 60 wt% and more preferably 20 to 50 wt% ZrO2; and to 80 wt% and more preferably 30 to 70 wt% SiO2
The sum of Li2O + ZrO2 + SiO2 is preferably greater than 50 wt%, more preferably greater than 80wt% and even more preferably greater than 95wt%.
Preferred lithium alkaline earth silicates include the crystalline and/or amorphous form of
Li2MgSiC>4, Li2CaSiC>4, LhSrSiCUand LhBaSiCUand combinations thereof.
A preferred composition of lithium alkaline earth silicates fibres comprise:
to 40wt% and more preferably 5 to 30wt% Li2O;
to 80 wt% and more preferably 20 to 50 wt% alkaline earth oxides; and to 60 wt% and more preferably 30 to 70 wt% SiO2
The alkaline earth oxides are preferably selected from MgO, CaO, BaO or SrO and combinations thereof.
The sum of Li2O + alkaline earth oxides + SiO2is preferably greater than 50 wt%, more preferably greater than 80wt% and even more preferably greater than 95wt%.
Preferred lithium manganates include the crystalline and/or amorphous form of Li2MnO3 and Li2MnC>4 and combinations thereof.
A preferred composition of lithium manganates fibres comprise:
to 40wt% and more preferably 5 to 30wt% Li2O; and to 80 wt% and more preferably 20 to 50 wt% MnO.
The sum of Li2O + MnO is preferably greater than 50 wt%, more preferably greater than 80wt% and even more preferably greater than 95wt%.
Preferred lithium phosphates include the crystalline and/or amorphous form of LiAIFPO4, LiAI(OH)PO4, LiFePO4, LiMnPO4, Li3AI2(PO4)3, Li9AI3P8O29, LiGe2(PO4)3, LiZrHf(PO4)3,
Lii+xAlxGe2-x(PO4)3 (where x is any number between 0 and 2), Ι_ίι+χΜχΤί2.χ(ΡΟ4)3 - (M = Al, Cr, Ga, Fe, Sc, In, Lu, Y, La and where x is any number between 0 and 2) and combinations thereof.
A preferred composition of lithium phosphate fibres comprise:
to 30wt% and more preferably 5 to 20wt% U2O; and to 80 wt% and more preferably 20 to 60 wt% P2O5;
to 70 wt% and more preferably 20 to 50 wt% ZrC>2 to 90 wt% and more preferably 20 to 60 wt% T1O2
The sum of U2O + P2O5 is preferably greater than 40wt%, more preferably greater than 60 wt% and most preferably greater than 80 wt%.
Preferred lithium titanates include the crystalline and/or amorphous form of Li4TiO4, 1_Ϊ2ΤΪ6θΐ3 LiTi2O4, Li2TiO3, Li2SrTieOi4, LiTiSi2O6 and combinations thereof.
A preferred composition of lithium titanates fibres comprise:
to 30wt% and more preferably 5 to 20wt% U2O; and to 90 wt% and more preferably 20 to 60 wt% T1O2
The sum of U2O + T1O2 is preferably greater than 40wt%, more preferably greater than 60 wt% and most preferably greater than 80 wt%.
Preferred lithium titanium phosphate include the crystalline and/or amorphous form of LiTiPOs and LiTi2(PO4)3 and combinations thereof.
A preferred composition of lithium titanium phosphate fibres comprise:
to 30wt% and more preferably 5 to 20wt% U2O; and to 80 wt% and more preferably 20 to 60 wt% P2O5;
to 90 wt% and more preferably 20 to 60 wt% T1O2
The sum of U2O + T1O2 + P2O5 is preferably greater than 50wt%, more preferably greater than 80 wt% and most preferably greater than 95 wt%.
Preferred lithium zirconium phosphate include the crystalline and/or amorphous form of
LiZr2(PO4)3 or LiZrPsOi2 and combinations thereof.
A preferred composition of lithium zirconium phosphate fibres comprise:
to 30wt% and more preferably 5 to 20wt% Li2O;
to 60 wt% and more preferably 20 to 50 wt% P2Os; and to 70 wt% and more preferably 30 to 50 wt% ZrO2
The sum of Li2O + ZrO2 + P2Os is preferably greater than 50wt%, more preferably greater than 80 wt% and most preferably greater than 95 wt%.
Preferred lithium lanthanum titanates and lithium lanthanum zirconates include the crystalline and/or amorphous form of Li?La3Zr20i2, Li3xLa2/3-xTiO3 and combinations thereof.
A preferred composition of lithium lanthanum titanates fibres comprise:
to 30wt% and more preferably 5 to 20wt% Li2O; and to 90 wt% and more preferably 20 to 50 wt% l_a2C>3 to 90 wt% and more preferably 20 to 60 wt% TiO2
The sum of Li2O + l_a2C>3+ TiO2is preferably greater than 50wt%, more preferably greater than 80 wt% and most preferably greater than 95 wt%.
A preferred composition of lithium lanthanum zirconate fibres comprise:
to 30wt% and more preferably 5 to 20wt% Li2O; and to 90 wt% and more preferably 20 to 50 wt% l_a2C>3 to 50 wt% and more preferably 20 to 40 wt% ZrO2
The sum of Li2O + l_a2C>3 + ZrO2 is preferably greater than 50wt%, more preferably greater than 80 wt% and most preferably greater than 95 wt%.
Other lithium ion conductive compounds which may be integrated into fibres, or form part of inorganic fillers/binders used in the formation of separators or composite electrolytes, include, but are not limited to:
1. Nitrides
i. Amorphous
a) UPON ii. Crystalline
a) U3N (alpha or beta)
2. Oxides
i. Amorphous
a) xLi2O.(1-x)SiO2 where x is between 0 and 1
b) xLi2O.(1-x)B2O3 where x is between 0 and 1 ii. Crystalline:
a) Lithium Superionic Conductors (LISICON) such as
a. Lii4A(BO4)4 where A = Zn, Zr, Cr or Sn and B = Ge, Si,
SorP
b. (1-x)Li4SiO4.xLi3PO4 where x is between 0 and 1
b) (Structure of) Sodium Superionic Conductors (NASICON) such as
a. Li(i+X)AxB2-x(PO4)3 where A = Al, Y, Ga, Cr, In, Fe, Sc or
La and B=Ti, Ta, Zr, Ge, Sn, Si, Fe, V or Hf and x is between 0 and 1
b. Main examples are LATP and LAGP
c) Perovskite
a. Li3xA(2/3)-xBO3 where A = La, Al, Mg, Fe or Ta and B =
Ti, Pr, Nb or Sr and x is between 0 and 2/3.
b. Main example is LLTO
d) Garnet
a. U3+XA3B2O12 where A = La, Ca, Sr, Ba or K and B =
Ta, Te, Nb or Zr and x is between 2 and 4 and is contingent upon the materials for A and B
b. Li7-xA3B2.xCxOi2 where A = La, Ca, Sr, Ba or K, where
B = Ta, Te, Nb or Zr, where C = Ta, Te, Nb or Zr and where x is between 0 and 2
c. Preferably LLZO (Li?La3Zr20i2)
3. Sulfides
i. Amorphous
a. xLi2S.(1-x)P2S5 where x is between 0 and 1
b. xLi2S.(1-x)AI2S3 where x is between 0 and 1
c. xLi2S.(1-x)SiS2 where x is between 0 and 1
d. LiPOS ii. Crystalline
1. LiioAB2Si2 where A is Ge, Sn or Pb and B is P, Si or Al
a. Preferably LiwGeP2Si2
4. Hydrides
i. Single complex anion of form Li(XHn) where XHn is a complex anion such as NH2, BH4 and AIH4 ii. Double complex anion of form Li(XHn).aLi(YHn) where XHn and YHn are identical or different complex anions such as NH2, BH4 and AIH4, and a is the ratio of their combination iii. Combination with halide - Li(XHn) - LiZ where XHn is a complex anion such as NH2, BH4 and AIH4 and Z is a halide such as CI-, Br- or I-.
iv. Main example is LiNH2.3LiBH4
5. Halides
i. Lil, spinel Li2Znl4 and anti-perovskite U3OCI
In some embodiments, the inorganic fibres are organic-inorganic hybrid fibres. Within this embodiment, the inorganic fibres preferably comprise at least 40wt%, more preferably at least 80wt% and even more preferably at least 90wt% inorganic matter. The inclusion of a small amount of polymer into the fibres can enhance mechanical properties without detrimentally effecting the fibre’s high temperature performance.
Crystalline form
The proportion of amorphous crystalline material may be adjusted through heat treatment techniques as known by those skilled in the art.
In some embodiments, the amorphous phase content of the fibres is in the range of 0 and 100 wt%, preferably greater than 0 and less than 90 wt% and more preferably greater than 30 wt% and less than 70 wt%.
In some embodiments, the fibres may have a crystalline content of at least 40 wt%, preferably at least 50 wt%, more preferably at least 70 wt% and even more preferably at least 90 wt%.
In some embodiments, the fibres may have a crystalline content of less than 50 wt%, preferably less than 30 wt%, more preferably less than 10 wt% and even more preferably less than 5 wt%. In a preferred embodiment, no crystalline content is detectable.
In some embodiments, the fibres have a crystalline surface layer and an amorphous core layer.
In embodiments comprising lithium aluminium silicates fibres, the inorganic fibres preferably comprise eucryptite (LiAISiCU), spodumene (LiAI(SiC>3)2 and/or petullite (LiAISiOw).
The Eucryptite content is preferably in the range of 10 to 90 wt%.
The Eucryptite content is preferably greater than the spodumene content or the petullite content.
Preferably, the spodumene content and the petullite content is less than 20 wt% and preferably less than 10 wt% and even more preferably less than 5 wt %.
Fibre dimensions for separators, electrolytes and matrices thereof
The fibre preferably has a geometric or arithmetic mean fibre diameter of less than 10.0 pm or 5.0 pm and more preferably less than 3.0 pm and even more preferably less than 2pm. Fibres are preferably of diameter of at least 0.2 pm or 0.3 pm or 0.5pm or 0.8 pm or 1.0 pm or 1.2 pm and even more preferably at least 1.4 pm to have sufficient mechanical strength and to be manufactured economically. This fibre diameter range is particularly suited in combination with liquid electrolytes. However, fibre mean diameter of 100nm or less may be possible, particularly if electrospun and incorporated into a solid electrolyte matrix. A low fibre diameter facilitates the production of a thinner separator layer and increases the ionic conductive surface area of the separator. The fibre is preferably cleaned of shot (> 43pm), with the shot content preferably less than 1.0 wt% and more preferably less than 0.5 wt%.
The geometric or arithmetic mean fibre length is preferably greater than 10 pm more preferably greater than 100 pm, even more preferably greater than 1 mm , yet even more preferably greater than 3 mm and most preferably greater than 5 mm. The geometric or arithmetic mean fibre length is preferably less than 100 mm, more preferably less than 25 mm and even more preferably less than 10 mm.
The fibre preferably has an aspect ratio of at least 3 or 10 or 20 or 30 and more preferably at least 100. For the purposes of the present invention, inorganic particles are defined as particles having an aspect ratio of less 3.
Ion Conductivity
For the purposes of the present invention, lithium ion conducting inorganic fibres are inorganic fibres that have an ionic conductivity greater than alumina-silicate fibres or alkaline earth silicate fibres. The inorganic fibres of the present invention preferably have an ionic conductivity at least 20%, more preferably at least 100% or at least 200% or at least 300% or at least 400% or at least 500% and even more preferably at least 1000% greater than:
• alumina-silicate fibres, in which the alumina and silicate content is preferably at least 95wt% and more preferably at least 99wt% of the fibre. Commercially available alumina-silicate fibres include Cerafibre™, Cerachem™, Alphawool™ HA and Alphawool™ LA;
• Alkaline earth silicate fibres, in which the silicate content is at least 50wt% and more preferably at least 70wt%, with an alkaline earth oxide content of preferably at least 20wt% and more preferably at least 30wt%. Commercially available alkaline earth silicate fibres include SuperWool™ XTand SuperWool™ HT.
Fibre ion conductivity may be determined using electrochemical impedance spectroscopy (EIS). The ionic conductivity at 30°C is preferably at least 1.0 x 10'6S cnr1or 5.0 x 10'6S cm1 or 6.0 x 10-6 S cm'1 or 7.0 x 10'6 S cm'1 or 8.0 x 10'6 S cm'1 or 9.0 x 10'6 S cm'1 or 1.0 x 10'5
S cm-1 or 1.2 x 10-5 S cm-1 or 1.4 x 10-5 S cm-1 or S cm-1 or 1.5 x 10’5 S cm-1 or 2.0 x 10_5S erm 1όγ 3.0 x 10-5 S cm’1 or 4.0 x 10’5 S erm1 or 5 x 10’5S erm1 or 1 x 10’4S erm1 or 5.0 x 10’4S cm'1 or 1.0 x 10'3S cm'1.
The ionic conductivity of electrolyte soaked fibres (for example with electrolyte 1M LiPF6 in EC/DEC (1:1 v/v)) of the present invention is preferably at least 1.0 mScrm1 more preferably at least 5.0 mScrm1, yet more preferably at least 10 mScrm1 and most preferably at least 100 mScrm1. Separators comprising the inorganic fibres preferably increases the conductivity of the electrolyte soaked separators by at least 5%, more preferably at least 10% and even more preferably 20% compared to electrolyte soaked conventional separators.
The ionic conductivity of separators may be determined by creating a cell (e.g. a blockingtype cell fabricated by the electrolyte soaked membrane placement between two electrodes (e.g. stainless steel or platinum), preferably in an inert gas filled glove box). Consequently, the impedance data of the cell was measured by an electrochemical workstation over a frequency range (e.g. 0.01 Hz to 10 kHz), preferably with an amplitude voltage of between 1mV and 20mV (e.g. 5 mV). The ionic conductivity of the fibres is preferably determined analogously, with an insulative polymer (e.g. PVDF) and inorganic fibre composite placed between the electrodes. The ionic conductivity attributable to the inorganic fibre portion of the composite may then be determined.
Consequently, the ionic conductivity (σ) may be calculated by the following equation:
σ = D/RS (4) where S is the contact area of the electrodes, R is the resistance of the separator which can be obtained from the AC impedance data and D is the thickness of the separator.
Fibre conductivity at 25°C is preferably of greater than 1.0 x 10_5S cnr1or 1.2 x 10_5S cm-1 or
1.5 x 10'5 S cm-1 or 2 x 10'5S cm-1 or 5 x 10'5S cm-1 or 1 x 10'4S cm-1 or 5 x 10'4S cm-1 or 1 x 10_3S cm-1. Testing is conducted in accordance to ASTM D257-14, ASTM D4496 or other suitable equivalent method relating to insulative and moderately conductive materials.
Mechanical properties
During the assembly of the battery and during their use, separators are subjected to a degree of mechanical and thermal stress.
Tensile strength
Preferably, membranes comprising fibres under the scope of the present invention comprise a tensile strength, on a wet and/or dry basis, of at least 1 MPa, more preferably at least 2 MPa, even more preferably at least 3 MPa and most preferably at least 4 MPa.
Shrinkage
The fibres preferably have a shrinkage of no more than 10.0 % or 5.0 % or 3.0 % and more preferably no more than 1.0% or 0.5% or 0.2% at 1000°C. At 1100°C the fibres have a shrinkage of preferably no more than 4.0% and preferably no more than 2.0% or 0.5%. At 1200°C the fibres have a shrinkage of preferably no more than 5.0% and preferably no more than 2.0% or 1.0%. Preferably, separators comprising the fibres have a similar shrinkage performance (i.e. within 50% of the performance of the fibres used therein.) Low shrinkage ensures that the resultant separator is able to separate the electrodes and avoid a short circuit within the battery even at elevated temperatures.
Applications
The fibres of the present invention preferably form part or all of a separator or part or all of solid electrolyte or part or all of an inorganic I organic electrolyte matrix within a lithium ion energy storage device, such as a battery or capacitor.
The fibres of the present invention may be manufactured via a variety of means including, but not limited to sol gel, melt spinning and electro-spinning techniques.
Separator
The lithium ion inorganic fibres are preferably integrated into a separator. The fibres preferably form a non-woven web from which the separator is produced. In one embodiment the fibres are substantially orientated in the same plane as the web, such that within a battery, the fibres are substantially parallel to the electrodes. In other embodiments, the fibres are randomly oriented.
In one embodiment, the configuration inorganic fibres forms a tortuous lithium ion pathway from the anode side of the separator to the cathode side. Preferably the inorganic fibres contact one or more adjacent fibres within the separator to form a plurality of lithium ion pathways. The separators preferably also comprise lithium ion conducting inorganic fillers. The fillers may be used to control the separator porosity in addition to creating a plurality of continuous ionic conductive pathways. Despite the tortuous pathways that the fibres produce, connection between fibres and inorganic particles enable lithium ion transfer bridges to be formed between fibres and particles thereby enabling more direct lithium ion transfer across the separator.
In a preferred embodiment, two or more inorganic fibres and/or inorganic particles form a lithium ion conductive pathway across the separator.
The composition of the separator preferably comprises:
• 5 to 100wt%, more preferably 30 to 98 wt%, even more preferably 40 to
95wt%, yet even more preferably 50 to 90wt% and most preferably between 60 and 80 wt% lithium ion conducting inorganic fibres;
• 0 to 95wt% more preferably 5 to 60 wt%, even more preferably 10 to 50 wt%, yet even more preferably 15 to 40 wt% and most preferably between 20 and 40 wt% lithium ion conducting inorganic particles; and • 0 to 50wt%; more preferably 3 to 20 wt% and even more preferably 5 to 10 wt% binder
In one embodiment the composition of the inorganic fibres are the same as the composition of the inorganic particles. For the purposes of the present invention, the “same composition” means specific oxide components are within 1wt% or 10% of each other, whichever is greater.
The inorganic particles preferably have a mean diameter of less than 100 microns and more preferably less than 50 microns, yet even more preferably less than 20 microns and more preferably less than 10 microns. The mean diameter of the particles is typically at least 10 nm and more preferably at least 100nm. A smaller particle size enables the separators to be thinner and increases the ionic conductive surface area of the separator.
The binder may be inorganic or organic. The inorganic binders preferably have a softening melting temperature below the softening temperature of the inorganic fibres. In some embodiments, the inorganic binder is a lithium ion conducting particle.
Suitable organic binders may be selected from the group consisting of polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polyethylene oxide (PEO), polytetrafluoroethylene, polyacrylate, styrene-butadiene rubber, and carboxymethylcellulose (CMC), and mixtures and copolymers thereof.
In one embodiment, the organic binders are preferably polymers having a relative high melting temperature (e.g. preferably >150°C and more preferably greater than 200°C) to enable the separator to still effectively function at elevated temperatures.
The separator preferably forms a composite membrane (or matrix) with a solid, gel or liquid electrolyte.
The ceramic fiber separator may be prepared by a traditional wet winding process. The lithium ion conducting fibres, were combined with a binder (for example carboxyl methyl cellulose (CMC)) and a dispersant (for example polyethylene oxide (PEO)) added. The proportion of the materials (e.g. weight ratio of 90:7:3 respectively) may be dissolved into an amount of distilled water under a continuous stir, whereas the viscosity of the solution may be controlled by the binder contents. Following stirring for 8 h, the mixed solution may be placed onto the forming wire to form a membrane, followed by overnight drying at 120 °C under vacuum. Consequently, the membrane thickness was controlled by an extended roller.
Alternatively, the separator may be made in accordance with the general methodology disclosed in US9637861, with the exception that the inorganic fibres of the present invention partially and preferably completely replace microfibers. Additionally, the nanofibers can be partially or completely replaced with fillers and/or binders. Fillers and/or binders are preferably added to control the porosity of the separator. The fillers and binders may also increase the surface area of lithium ion conductive pathways. In one embodiment, organic binders are used to bind lithium ion conductive particles within a non-woven fibrous web.
The resultant separators preferably exhibit one or more of the following characteristics:
• porosity ranging from about 70%to about 98%;
• peel strength from about 0.03 kN/m to about 0.50 kN/m;
• an ASTM Gurley Number in the range of about 30 to 150 sec. ASTM Gurley Number refers to the time it takes for 10 cc of air at 12.2 inches of water to pass through one square inch of membrane;
• a liquid absorbency ranging from about 200%to about 1300%.
• an areal density ranging from about 0.2 g/m2 to about 3 g/m2.
• A thickness of less than 100 pm preferably less than 50 pm and more preferably less than 30 pm
In batteries systems in which the inorganic fibres have a similar (e.g. within 25%) or greater lithium ion conductivity than the electrolyte, then the optimal design parameter shift towards separators with lower open porosity (e.g. preferably less than 70% and even more preferably less than 50%); and increased thickness (e.g. greater than_100 pm and even more preferably greater than 500 pm).
Polymer component
In some embodiments, the separator preferably comprises a polymer component.
The polymer component may function to assist in the formation of the separator (e.g. action as a binder of the inorganic fibres) and/or enhance the properties of the separator (e.g. toughness and/or enhance porosity).
To avoid the polymer component negatively affecting the functioning of the separator (e.g. safety or conductivity), the proportion of the polymer component is preferably in the range of 0.1 wt% to 50wt%, more preferably 2wt% to 40wt% and even more preferably 5wt% and 25wt%. In preferred embodiments, the polymer content is less than 20wt%, more preferably less than 10wt% and yet even more preferably less than 5wt%.
In embodiments in which the inorganic fibres forms part of a fibre I solid (e.g. polymer) or liquid electrolyte matrix, the proportion of polymers is preferably at least 60 wt%, more preferably at least 80 wt% and even more preferably at least 85 wt% and yet even more preferably at least 90 wt%.
The lower proportion of polymer in the separator compared to the matrix is due to the separator having a higher porosity (or void space) to absorb a liquid electrolyte.
The polymer may comprise polyvinylidene fluoride (PVDF), poly (vinylidene fluoridehexafluoropropylene) (PVDF-HFP)), polymethyl methacrylate (PMMA) , polyacrylonitrile (PAN) , polyimide (PI) , polyvinyl pyrrolidone (PVP) , polyethylene oxide (PEO) , polyvinyl alcohol (PVA), sodium carboxymethyl cellulose (Na-CMC) , styrene-butadiene rubber (SBR) and combinations thereof.
In a preferred embodiment, the polymer component forms part of a hydrid organic/inorganic fiber, preferably produced via electro-spinning techniques, such as those disclosed in US 15 8,846,199.
Electrochemical device components
The chemically and thermally inert nature of the inorganic fibres enable them to be compatible to most battery systems.
Electrolyte
Due to its high temperature stability, the inorganic fibres of the present invention may be advantageously combined with ionic liquid based electrolyte, either solvent, gel or polymer.
The ionic liquids preferably contain exclusively or substantially ions. Examples of cations include those which can be in alkylated form, such as imidazolium, pyridinium, pyrrolidinium, guanidinium, uronium, thiuronium, piperidinium, morpholinium, sulfonium, ammonium, and phosphonium cations. Examples of anions which can be used include halide, tetrafluoroborate, trifluoroacetate, triflate, hexafluorophosphate, phosphinate, and tosylate anions.
Exemplary ionic liquids include the following: N-methyl-N-propylpiperidinium bis(trifluoromethylsulfonyl)imide, N-methyl-N-butylpyrrolidinium bis(trifluoromethylsulfonyl)imide, N-butyl-N-trimethylammonium bis(trifluoromethylsulfonyl)imide, triethylsulfonium bis(trifluoromethylsulfonyl)imide, and N, Ndiethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide.
The electrolyte is preferably non-aqueous solvent, polymer or gel. The solvent is capable of being used for the non-aqueous electrolytic solution of the present invention and is not particularly limited as long as the electrolyte salt can be dissolved or dispersed in it, and can be any one of many publicly known solvents used for a battery, for example, non-aqueous solvents such as cyclic carbonates described later and a solvent other than a cyclic carbonate; and a medium such as a polymer or a polymer gel which is used in place of the solvent, can be used.
As the non-aqueous solvent, it is preferred that such a solvent exhibits high dielectric constant, can readily dissolve an electrolyte salt, has a boiling point of not less than 60°C., and is electrochemically stable. The non-aqueous solvent is more preferably a non-aqueous organic solvent of which water content is small. Such a non-aqueous organic solvent is exemplified by an ether solvent such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2,6-dimethyltetrahydrofuran, tetrahydropyran, crown ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,4-dioxane and 1,3-dioxolan; a chain carbonate ester solvent such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, diphenyl carbonate and methyl phenyl carbonate; a saturated cyclic carbonate solvent such as ethylene carbonate, propylene carbonate, 2, 3-dimethylethylene carbonate (i.e. 2,3-butanediyl carbonate), 1,2-butylene carbonate and erythritan carbonate; a cyclic carbonate solvent having an unsaturated bond, such as vinylene carbonate, methylvinylene carbonate (MVC; i.e., 4-methyl-1,3-dioxole-2one), ethylvinylene carbonate (EVC; i.e., 4-ethyl-1,3-dioxole-2-one), 2-vinylethylene carbonate (i.e., 4-vinyl-1,3-dioxolane-2-one) and phenylethylene carbonate (i.e., 4-phenyl1,3-dioxolane-2-one); a fluorine-containing cyclic carbonate solvent such as fluoroethylene carbonate, 4,5-difluoroethylene carbonate and trifluoropropylene carbonate; an aromatic carboxylate ester solvent such as methyl benzoate and ethyl benzoate; a lactone solvent such as .gamma.-butyrolactone, .gamma.-valerolactone and .delta.-valerolactone; a phosphate ester solvent such as trimethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate and triethyl phosphate; a nitrile solvent such as acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, adiponitrile, 2-methylglutaronitrile, valeronitrile, butyronitrile and isobutyronitrile; a sulfur compound solvent such as dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, sulfolane, 3-methylsulfolane and 2,4-dimethylsulfolane; an aromatic nitrile solvent such as benzonitrile and tolunitrile; nitromethane, 1,3-dimethyl-2imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1 H)-pyrimidinone, 3-methyl-2oxazolidinone and the like.
Solid Polymer Electrolytes (SPE) may include amorphous or semi-crystalline PEO, PAN, PVC, PVDF, PMMA, P(VDF-HFP). In a preferred embodiment the SPE comprises PEO. Suitable crystalline SPE include PEOe:LiAF6 where A is P, As or Sb. Ina preferred embodiment the SPE comprises PEOe:LiPF6.
Composite Solid Electrolytes (CSE) may include SPE and non-Li based materials such as TiO2, ZrO2, AI2O3, Metal Organic Framework (MOF’s), CNT’s, grapheme. Alternative SPEs may be combined with lithium conducting inorganic electrolytes, preferably in the form of fibres. Preferred embodiments include SPEs combined with LISICON, NASICON, Perovskite, Garnet, thio-LISICON or combinations thereof.
Among the exemplified solvents, a carbonate solvent such as a chain carbonate ester solvent, and a cyclic carbonate ester solvent, a lactone solvent and an ether solvent are preferred, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, .gamma.-butyrolactone and .gamma.-valerolactone are more preferred, a carbonate solvent such as dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate is further more preferred. One of the above-described other solvents may be used alone, or two or more other solvents may be used in combination.
When the above-mentioned polymer or polymer gel is used in place of a solvent, one of the following methods may be used. That is, a method in which a solution obtained by dissolving an electrolyte salt in one of the above-mentioned non-aqueous solvents is added dropwise to a polymer formed into a film by a publicly known method to impregnate the polymer with the electrolyte salt and the non-aqueous solvent or to support the electrolyte salt and the non-aqueous solvent; a method in which a polymer and an electrolyte salt are melted at a temperature of a melting point of the polymer or higher, mixed, and then formed into a film, and the film is impregnated with a non-aqueous solvent (these are gel electrolytes); a method in which a non-aqueous electrolytic solution is obtained by dissolving an electrolyte salt in an organic solvent in advance is mixed with a polymer, and the resulting mixture is formed into a film by a casting method or a coating method, and an organic solvent is volatilized; and a method in which a polymer and an electrolyte salt are melted at a temperature of a melting point of the polymer or higher, mixed, and then molded (intrinsic polymer electrolyte) are exemplified.
Lithium salt
Suitable lithium salts include LiPF6, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethylsulfonate, lithium tetrafluoroborate, lithium bromide, and lithium hexafluoroantimonate, and mixtures thereof. The salts can be used in combination with other salts including, without limitation, hydrolyzable salts such as LiPFein any suitable amounts. Typically, the amount of such additional salts ranges from about 0.01 M to about 1.5 M.
Electrodes
Electrochemical devices incorporating the lithium ion conducting inorganic fibres can employ any suitable cathode and anode. In forming a lithium secondary battery typically the anodes are non-metallic and can be based upon non-graphitizing carbon, natural or artificial graphite carbon, or tin oxide, silicon, or germanium compounds.
The positive electrodes for use in lithium secondary batteries typically are based upon a lithium composite oxide with a transition metal such as cobalt, nickel, manganese, among others and mixtures thereof, or a lithium composite oxide, part of whose lithium sites or transition metal sites are replaced with cobalt, nickel, manganese, aluminum, boron, magnesium, iron, copper, among others and mixtures thereof or iron complex compounds such as ferrocyan blue, berlin green, among others and mixtures thereof. Specific examples of lithium composites for use as positive electrodes include LiNi0.8Co0.15AI0.05O2, LiNio.5Coo.2Mno.3O2, LiNii-xCoxO2 (where x is a number between 0 and 1) and lithium manganese spinel, LiMn2O4.
References to a or an should be interpreted broadly to encompass one or more of the features specified. Thus, in the case of a fibre, the device may include one or more fibres.
In this application, except where the context requires otherwise due to express language or necessary implication, the word comprise or variations such as comprises or comprising is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features.
Brief description of the Figures
Figure 1 is a XRD diagram for Sample 1, after being fired at 1000°C.
Figure 2 is a XRD diagram for Sample 4, after being fired at 1000°C; and
Figure 3 is a XRD diagram for Sample 5, after being fired at 900°C
Detailed Description
For the avoidance of doubt it should be noted that in the present specification the term “comprise” in relation to a composition is taken to have the meaning of include, contain, or embrace, and to permit other ingredients to be present. The terms “comprises” and “comprising” are to be understood in like manner. It should also be noted that no claim is made to any composition in which the sum of the components exceeds 100%.
Where a patent or other document is referred to herein, its content is incorporated herein by reference to the extent permissible under national law.
Further it should be understood that usage in compositions of the names of oxides [e.g. alumina, silica, quicklime, calcia, strontia] does not imply that these materials are supplied as such, but refers to the composition of the final fibre expressing the relevant elements as oxides. The materials concerned may be provided in whole or in part as mixed oxides, compounded with fugitive components [e.g. supplied as carbonates] or indeed as non-oxide components [e.g. as halides or sulphides].
Examples
Fibres were formed using the sol-gel or melt spinning method
Sol-Gel Method
Except for such differences as highlighted below, the manufacturing method was similar to that of the fibres disclosed in PCT application no. WO 2007/054697. The precursors used were composed of a base sol to which was added precursors for the desired fibre composition. Where required, the following precursors were used:
Aluminium chlorohydrate was used as the source of alumina.
Lithium chloride and lithium dihydrogen phosphate were used as the source of lithium oxide.
Lanthanum nitrate hydrate was used as the source of lanthanum oxide.
Zirconium chloride and Zirconium oxynitrate were used as the source of zirconia.
A mixture of siloxane and colloidal silica sol acted as a source of silica. The precursors used for the preparation of the base sol for the production of the fibre in the present invention can be accomplished by other conventional methods known in the art. These include the use of inorganic oxy compounds, alkoxides, and chlorides.
The invention is not limited to any particular method of forming the fibres from the sol, and other methods [e.g. rotary or centrifugal formation of fibres; drawing; air jet attenuation; electrospinning may be used. The compositions described herein and other alkaline earth silicate fibres may also be made by melt methods, and such fibres may avoid problems that flow from formation by a sol-gel route.
The process used experimentally involved a fibre blowing system where sol is forced through small orifices (typically ~0.3mm) using pressure generated using compressed or pressurised air. Surrounding each orifice is a shroud of air to dry and draw the fibres. Alternative methods which may be used to produce sol-gel fibres include:
• Sol is extruded through 300 x 0.2 mm holes spaced evenly around the periphery of a disc rotating at 2600 r.p.m. Air at 15°C and 45% relative humidity is blown through an annular orifice past the disc to attenuate the sol streams. Hot air at 160 - 200°C is blown through a further annular orifice outside the fiberising air annular orifice to dry the sol streams into green fibre.
• A spinning disc of a closed cup design with rows of holes around the circumference (typically ~0.5mm diameter), the sol being fed to the spinner through the shaft.
• Feeding a liquid sol onto a rapidly spinning shallow cup having inclined sides. Fiberisation has been demonstrated from 3,000rpm up to 15,000rpm.
The applicant previously used a method in which sol was ejected from the lip of the cup by centrifugal force, forming thin streams of material. As the ejected material left the cup it passed through a stream of hot air which dried and gelled the sol to form an unfired fibre. The temperature of this air was measured using a thermocouple positioned in the hot air flow just above the spinning cup. The air temperature used for the majority of examples was ~60°C. Some sols were fiberised using drying air up to ~80°C. The air temperature needs to be selected to meet the viscosity and drying characteristics of the sol and the additives present. Typically temperatures of 30°C to 150°C may be used as appropriate. Any other suitable means for drying the fibre may be employed, for example, by circulating dehumidified air or gas around the fibre.
The applicant presently uses a process in which sol is extruded through 0.4 mm diameter holes with a spacing of 3 mm using compressed air to provide back pressure. The liquid streams are then attenuated by airstreams either side of the sol streams and broadly parallel with them.
The air streams are at a distance of 1 mm from the sol streams. The air pressure used is 0.1 bar and the resultant air velocity about 120 m/s. The air is humidified and cooled to maintain 25-35°C and a relative humidity of between 45 and 65%. The chamber into which the sol streams are attenuated is kept at a temperature of between 90 and 100°C measured at a distance 500 mm from the fiberising heads.
It has been discovered that the process of drying the fibres can have a significant effect on their subsequent physical properties. In the event fibres are not properly dried on emergence, “kinks” can appear in the fibres produced and mechanical resilience suffers accordingly.
Beneficially, it has been discovered that the spacing of the fibre streams involved has an effect on drying; a 3mm spacing between nozzles/holes/orifices/points of origin for fibre streams can ensure that sufficient airflow exists to allow for proper drying.
The fibres were collected in alumina kiln trays and heat treated by placing the tray in a kiln and firing. Superior results were obtained when the fibres were fired at 900°C for an hour, allowed to cool, and subsequently fired at 1050-1250°C (usually 1150°C) for an hour (with a 100°C/hr ramp rate). As an alternative, the fibres can also be fired through a tunnel kiln with a peak temperature up to 1250°C over a time period of up to 12 hours.
Melt spinning method
Fibres according to the invention have been produced by spinning [made from the melt by forming a molten stream and converting the stream into fibre by permitting the stream to contact one or more spinning wheels]; at the applicant’s research facilities in Bromborough, England by spinning or alternatively by blowing [fibres made from the melt by forming a molten stream and converting the stream into fibre by using an air blast directed at the stream].
Samples
Samples 1 to 4 were formed by the melt method as previously described and Sample 5 was formed by the sol-gel method as previously described.
Table 1
Sample Stoichiometric Composition Li2O Target/Actual Wt% AI2O3 Target/Actual Wt% SiO2 Target/Actual Wt% CaO T arget/Actual Wt%
1 LiAISiO4 11.86/10.12 40.46/38.27 47.68/51.61 -
2 LiAISi2O6 8.03/7.33 27.40/22.82 64.58/69.84 -
3 LisAhSiOs 17.38/17.13 59.32/58.17 23.30/24.70 -
4 Li2CaSiO4 20.46/19.71 - 41.14/44.76 -
5 LiAISiO4 11.86/9.63 40.46/40.20 47.68/51.61 38.40/35.53
Fibre shrinkage
Tests were performed by making a vacuum formed board in a 75mm square template (thickness is dependent on amount of sample). The board is measured on all 4 sides using calibrated Vernier calipers at least twice so that an average is used. The board is then heated at a steady rate of 300°C/hr and held at the desired temperature for 24 hours before cooling. The 4 sides are measured again and the measurements compared to the initial in accordance with ISO 10635.
Sample 1 results:
Table 2
Temperature °C % shrinkage
25 0
1000 0.05
1100 0.3
1200 0.8
1250 2.0
1300 7.9
Fibre diameter
Fibre diameters were determined from SEM images of a sample taken at x1500 magnification using auto focus. The software macro sweeps across the sample taking 350 images. The images are then analysed using the Scandium software package where any fibre with an aspect ratio greater than 3:1 that lies on the central line of the image is measured. All samples below this aspect ratio are not considered fibres.
Sample 4 results:
Geometric mean diameter: 2.27 pm
Arithmetic mean diameter: 2.47 pm
Standard Deviation: 1.27 pm
XRD
XRD measurements were taken of:
• Sample 1, after being fired at 1000°C;
• Sample 4, after being fired at 1000°C;
• Sample 5, after being fired at 900°C
The results indicated that:
Sample 1 contained eucryptite (LiAISiCU) (peak intensity score: 86).
Sample 4 contained Li2CaSiO4, Li2Ca2Si2O7 and Li2SiC>3 (peak intensity scores 52, 33 and 25)
Sample 5 contained eucryptite (LiAISiCU) (peak intensity score: 76)
Reflective of the lower peak intensity score and the raised background at low 2Θ (i.e. <10°),
Sample 5 had a greater amorphous content relative to Sample 1.
Ionic Conductivity
Conductivity measurements may be carried out using A.C. impedance spectroscopy (e.g.
Hewlett Packard 4192A Impedance Analyser) in the range from 0.1 to 100 kHz.
Table 3
Sample No. Nominal Stoichiometric Composition or Trade Name Method Ionic Conductivity
1 LiAISiCU Melt >1.0 x IO’6S cm’1
2 LiAISi2C>6 Melt >1.0 x 10-6 S cm-1
3 Li3AI3SiOs Sol gel >1.0 x 10-6 S cm’1
4 Li2CaSiC>4 Melt >1.0 x 10-6 S cm’1
5 LiAISiCU Sol gel >1.0 x 10-6 S cm’1
6 Li2SiO3 Melt >1.0 x 10-6 S cm-1
7 Li2SrSiC>4 Melt >1.0 x 10-6 S cm’1
8 Li2BaSiC>4 Melt >1.0 x 10-6 S cm-1
9 Li4ZrSi2O8 Melt >1.0 x 10-6 S cm-1
10 LiZr2(PO4)3 Sol gel >1.0 x 10-6 S cm’1
11 LiTi2(PO4)3 Sol gel >1.0 x 10-6 S cm-1
12 Li3xLa2/3-xTiO3 Sol gel >1.0 x 10-6 S cm’1
13 Li7La3Zr20i2 Sol gel >1.0 x 10-6 S cm’1
C-1 Cerafibre™ - <1.0 x 10-6 S cm-1
C-2 Cerachem™ - <1.0 x 10-6 S cm’1
C-3 Alphawool™ HA - <1.0 x 10-6 S cm-1
C-4 Alphawool™ HA - <1.0 x 10-6 S cm’1
C-5 Superwool™ HT - <1.0 x 10-6 S cm-1
C-5 Superwool ™ XT - <1.0 x 10-6 S cm’1
The above inorganic fibre samples (randomly aligned) have been prepared (or are in preparation) for testing of their ionic conductivity. It is expected that all samples will have a greater conductivity against a reference alumina-silicate (randomly aligned) fibre and further 5 it is expected that the conductivity of the fibres will be at least greater than 1.0 x 10-6 S cm-1 at 30°C or room temperature.
This invention has been described herein in considerable detail to provide those skilled in the art with information relevant to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the invention can be carried out by different equipment, materials and devices, and that various modifications, both as to the equipment and operating procedures, can be accomplished without departing from the scope of the invention itself.

Claims (40)

1. A separator for an electrochemical device comprising lithium ion conducting inorganic fibres.
2. The separator according to claim 1, wherein the inorganic fibres comprise a lithium content of greater than 1.0 wt%.
3. The separator of claim 1 or 2 comprising:
5 to 100 wt% lithium ionic conducting inorganic fibres;
0 to 95 wt% lithium ionic conducting inorganic particles; and
0 to 50 wt% binder.
4. The separator of claim 3, comprising:
50 to 100 wt% lithium ionic conducting inorganic fibres;
10 to 50 wt% lithium ionic conducting inorganic particles; and
0 to 20 wt% binder.
5. The separator of claim 3 or 4, wherein the inorganic content is at least 90 wt%.
6. The separator according to any one of claims 3 to 5, wherein the two or more inorganic fibres and/or inorganic particles form a lithium ion conductive pathway across the separator.
7. The separator according to any one of the preceding claims comprising an open porosity of between 70 and 98%.
8. The separator device according to any one of the preceding claims, wherein the inorganic fibres comprise one or more crystalline or amorphous forms of lithium oxide, lithium silicate, lithium aluminate, lithium aluminium silicates, lithium borates, lithium zirconium silicates, lithium alkaline earth silicates, lithium phosphates, lithium zirconium/titanium phosphates and lithium lanthanum zirconates/titanates.
9. The separator according to claim 8, wherein the inorganic fibres comprise one of more crystalline or amorphous forms of lithium aluminium silicates, lithium alkaline earth silicates, lithium zirconium silicates, lithium zirconium/titanium phosphates and lithium lanthanum zirconates/titanates.
10. The separator according to claim 9, wherein the inorganic fibres comprise one or more crystalline or amorphous forms of LiAISiCU, LiAISi2O6, Li2CaSiO4, LiAISiCU, Li2SiO3, Li2SrSiO4, Li2BaSiO4, Li4ZrSi20s, Li2AI3SiO8, LiZr2(PO4)3, LiTi2(PO4)3, Li3xLa2/3-xTiO3 and Li7La3Zr20i2.
11. The separator according to any one of claims 8 to 10, wherein the composition of the inorganic fibre is within 25% of the stoichiometric amounts.
12. The separator according to any one of the preceding claims, wherein the inorganic fibres comprise U2O, AI2O3 and S1O2.
13. The separator according to any one of the preceding claims, wherein the sum of U2O, AI2O3 and S1O2 in the inorganic fibres is at least 50wt%.
14. The separator according to any one of the preceding claims, wherein the inorganic fibres comprise:
4 to 15wt% U2O;
15 to 65 wt% AI2O3; and
20 to 80 wt% SiO2
15. The separator according to any one of the preceding claims, wherein the sum of L12O + AI2O3 + S1O2 in the inorganic fibre is greater than 90 wt%.
16. The separator according to any one of the preceding claims, wherein the inorganic fibres comprise eucryptite (LiAISiCU).
17. The separator according to any one of the preceding claims, wherein the inorganic fibres comprise spodumene (UAI(SiC>3)2.
18. The separator according to any one of the preceding claims, wherein the inorganic fibres comprise petullite (LiAISi40w).
19. The separator according to any one of the preceding claims, wherein the Eucryptite (LiAISiCU) content is in the range of 10 to 90 wt%.
20. The separator according to any one of the preceding claims, wherein the Eucryptite (LiAISiCU) content is greater than the spodumene content or the petullite content.
21. The separator according to any one of the preceding claims wherein the spodumene content and the petullite content is less than 20 wt% and preferably less than 10 wt% and even more preferably less than 5 wt %.
22. The separator according to any one of the preceding claims, wherein amorphous phase content of the fibres is greater than between 0 and 50 wt%.
23. The separator according to any one of the preceding claims, wherein the geometric fibre diameter is less than 10 microns.
24. The separator according to any one of the preceding claims, wherein the geometric fibre diameter is less than 5 microns.
25. The separator according to any one of the preceding claims, wherein the geometric fibre diameter is less than 3 microns.
26. The separator according to any one of the preceding claims, wherein the geometric fibre diameter is less than 2.5 microns and greater than 0.5 microns.
27. The separator according to any one of the preceding claims, wherein the fibre has an aspect ratio of at least 10 and more preferably at least 100.
28. The separator according to any one of the preceding claims, wherein the fibre has an ionic conductivity of greater than 1.0 x 10-6 S cm-1 at 30°C.
29. The separator according to any one of the preceding claims, wherein the fibre has an ionic conductivity of greater than 5.0 x 10-6 S cm-1 at 30°C.
30. The separator according to any one of the preceding claims, wherein the fibre has an ionic conductivity of greater than 1.0 x 10-5 S cm-1 at 30°C.
31. The separator according to any one of the preceding claims, wherein the separator has a maximum operating temperature of at least 1000°C.
32. A separator according to any one of the preceding claims, wherein the separator has a shrinkage of no more than 3.0% at 1000°C.
33. An electrochemical device comprising an electrolyte and a separator according to any one of the previous claims.
34. The electrochemical device according to claim 33, wherein the separator has a maximum operating temperature greater than the electrolyte’s maximum operating temperature.
35. A process for the production of inorganic fibres as defined in any one of the preceding claims using sol-gel, melt spinning or electro-spinning techniques.
36. The process according to claim 35, wherein the inorganic fibres are further heat treated to adjust the proportion of crystalline and amorphous phases.
37. Inorganic fibre as defined in any one of claims 1 to 32.
38. Inorganic fibres according to claim 37, wherein the fibre shrinkage is no more than 3.0% at 1000°C.
39. Inorganic fibre as defined in any one of claims 1 to 32, 37 and 38 for use in a separator.
40. Inorganic fibre according to claim 39, wherein the inorganic content is greater than 90wt%.
GB1801684.0A 2018-02-01 2018-02-01 Electrochemical device and inorganic fibres for use therein Withdrawn GB2570678A (en)

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CN201980009381.0A CN111630688A (en) 2018-02-01 2019-01-25 Energy storage device and ion-conductive composition used therein
EP19702698.2A EP3747067A1 (en) 2018-02-01 2019-01-25 Energy storage device and ionic conducting composition for use therein
KR1020207021651A KR20200112855A (en) 2018-02-01 2019-01-25 Energy storage device and ion conductive composition for use therein
PCT/GB2019/050222 WO2019150083A1 (en) 2018-02-01 2019-01-25 Energy storage device and ionic conducting composition for use therein
GB1901343.2A GB2568613B (en) 2018-02-01 2019-01-31 Energy storage device and ionic conducting composition for use therein
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